1. Field of the Invention
The present invention relates to an inlet housing for centrifugal pumps. More specifically, the present invention relates to an inlet housing for tubular-type pumps, and the inlet housing includes a flange for connecting to a pump housing and an inlet funnel.
2. Description of the Related Art
Nozzle-shaped inlet housing parts can be used to even out the velocity distribution, especially for vertically positioned tubular-type pumps (see KSB Centrifugal Pump Lexicon, 3rd Edition, Frankenthal 1989, Pages 86, 163, 164). Such an inlet housing is usually called an inlet nozzle or an inlet valve. To minimize the pressure loss as much as possible, the shape of the inlet nozzle is calculated on the basis of the operating point of the transport stream Q.sub.N. Pumps designed in this way also function satisfactorily if the transport stream is reduced to 0.7 Q.sub.N. However, below this operating point, disturbances occur in the infeed since the back-flow from the impeller reaches the anti-vortex cross or the pre-rotation regulator.
Even though the inlet housing evens out the velocity distribution, the inlet water level always must have a guaranteed minimum height, called the overlap, in order to keep the inflow free of inlet vortices which could draw-in air. The inlet velocity at the inlet housing here is an essential determining variable for the creation of an inlet vortex. The greater the inlet velocity, the greater also must be the overlap. The absence of inlet vortices which draw-in air is the most important precondition for trouble-free, long-term operation of the pump.
A section of the structure called the inlet chamber, is connected directly in front of the pump in an attempt to produce a vortex-free inflow that is evened out on all sides. The foundation depth of the inlet chamber, to provide the necessary overlap and to maintain a minimum distance to the floor of the inlet chamber, is a decisive factor influencing the cost of erecting such systems.